Fix highliting breakpoint line number
Fix setting breakpoints - apparently the setting has to be in package DB
Redraw breakpoints after redrawing the code window
fix bug when collecting stack frames
When the debugged program exits, regain control and alert the user
Add an "Exit" button to the controls and a handler for it
Avoid stepping into the END block when the user clicks stepin/stepover at the end of the program
save/restore important globals when inside the debugger code